import express, { Request, Response } from 'express';
import { McpServer } from '../../server/mcp.js';
import { SSEServerTransport } from '../../server/sse.js';
import { z } from 'zod';
import { CallToolResult } from '../../types.js';

/**
 * This example server demonstrates the deprecated HTTP+SSE transport 
 * (protocol version 2024-11-05). It mainly used for testing backward compatible clients.
 * 
 * The server exposes two endpoints:
 * - /mcp: For establishing the SSE stream (GET)
 * - /messages: For receiving client messages (POST)
 * 
 */

// Create an MCP server instance
const server = new McpServer({
  name: 'simple-sse-server',
  version: '1.0.0',
}, { capabilities: { logging: {} } });

server.tool(
  'start-notification-stream',
  'Starts sending periodic notifications',
  {
    interval: z.number().describe('Interval in milliseconds between notifications').default(1000),
    count: z.number().describe('Number of notifications to send').default(10),
  },
  async ({ interval, count }, { sendNotification }): Promise<CallToolResult> => {
    const sleep = (ms: number) => new Promise(resolve => setTimeout(resolve, ms));
    let counter = 0;

    // Send the initial notification
    await sendNotification({
      method: "notifications/message",
      params: {
        level: "info",
        data: `Starting notification stream with ${count} messages every ${interval}ms`
      }
    });

    // Send periodic notifications
    while (counter < count) {
      counter++;
      await sleep(interval);

      try {
        await sendNotification({
          method: "notifications/message",
          params: {
            level: "info",
            data: `Notification #${counter} at ${new Date().toISOString()}`
          }
        });
      }
      catch (error) {
        console.error("Error sending notification:", error);
      }
    }

    return {
      content: [
        {
          type: 'text',
          text: `Completed sending ${count} notifications every ${interval}ms`,
        }
      ],
    };
  }
);

const app = express();
app.use(express.json());

// Store transports by session ID
const transports: Record<string, SSEServerTransport> = {};

// SSE endpoint for establishing the stream
app.get('/mcp', async (req: Request, res: Response) => {
  console.log('Received GET request to /sse (establishing SSE stream)');

  try {
    // Create a new SSE transport for the client
    // The endpoint for POST messages is '/messages'
    const transport = new SSEServerTransport('/messages', res);

    // Store the transport by session ID
    const sessionId = transport.sessionId;
    transports[sessionId] = transport;

    // Set up onclose handler to clean up transport when closed
    transport.onclose = () => {
      console.log(`SSE transport closed for session ${sessionId}`);
      delete transports[sessionId];
    };

    // Connect the transport to the MCP server
    await server.connect(transport);

    // Start the SSE transport to begin streaming
    // This sends an initial 'endpoint' event with the session ID in the URL
    await transport.start();

    console.log(`Established SSE stream with session ID: ${sessionId}`);
  } catch (error) {
    console.error('Error establishing SSE stream:', error);
    if (!res.headersSent) {
      res.status(500).send('Error establishing SSE stream');
    }
  }
});

// Messages endpoint for receiving client JSON-RPC requests
app.post('/messages', async (req: Request, res: Response) => {
  console.log('Received POST request to /messages');

  // Extract session ID from URL query parameter
  // In the SSE protocol, this is added by the client based on the endpoint event
  const sessionId = req.query.sessionId as string | undefined;

  if (!sessionId) {
    console.error('No session ID provided in request URL');
    res.status(400).send('Missing sessionId parameter');
    return;
  }

  const transport = transports[sessionId];
  if (!transport) {
    console.error(`No active transport found for session ID: ${sessionId}`);
    res.status(404).send('Session not found');
    return;
  }

  try {
    // Handle the POST message with the transport
    await transport.handlePostMessage(req, res, req.body);
  } catch (error) {
    console.error('Error handling request:', error);
    if (!res.headersSent) {
      res.status(500).send('Error handling request');
    }
  }
});

// Start the server
const PORT = 3000;
app.listen(PORT, () => {
  console.log(`Simple SSE Server (deprecated protocol version 2024-11-05) listening on port ${PORT}`);
});

// Handle server shutdown
process.on('SIGINT', async () => {
  console.log('Shutting down server...');

  // Close all active transports to properly clean up resources
  for (const sessionId in transports) {
    try {
      console.log(`Closing transport for session ${sessionId}`);
      await transports[sessionId].close();
      delete transports[sessionId];
    } catch (error) {
      console.error(`Error closing transport for session ${sessionId}:`, error);
    }
  }
  await server.close();
  console.log('Server shutdown complete');
  process.exit(0);
});